The disclosure of Japanese Patent Application No. 2000-402888 filed on Dec. 28, 2000, including the specification, drawings and abstract thereof, is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a control apparatus of a hybrid vehicle equipped with an internal combustion engine and a motor-generator and, more particularly, to a control apparatus of a hybrid vehicle for performing a torque reducing control at the time of a speed shift.
2. Description of the Related Art
With regard to automatic transmission-equipped vehicles, it is known that a torque reducing control is performed for the purpose of reducing the shift shock occurring during a speed shift.
In order to reduce the shift shock during a speed shift, it is effective to create a smooth semi-clutch state by reducing the working pressure on the clutch. However, reducing the working pressure of the clutch involves a drawback of a prolonged shift duration. Therefore, the engine torque is reduced at the time of a speed shift through an engine torque reducing control so as to lessen the shift shock without causing a prolonged shift duration.
In order to reduce the engine torque, it is a normal practice to employ a method in which the engine ignition timing is changed. That is, the engine torque is reduced through a generally-termed engine ignition timing-retarding control.
However, since the engine ignition timing-retarding control changes the fuel ignition timing from an optimal timing, the state of exhaust gas deteriorates during the timing-retarding control though the deterioration may last only for a short time.
This problem also occurs in hybrid vehicles equipped with an internal combustion engine and a motor-generator as drive power sources.
An object of the invention is to provide a control apparatus of a hybrid vehicle, which prevent deterioration of auto emission occurred by the torque reduction control in a hybrid vehicle.